/************************************************************************************[SimpSolver.h]
MiniSat -- Copyright (c) 2006,      Niklas Een, Niklas Sorensson
		   Copyright (c) 2007-2010, Niklas Sorensson

Chanseok Oh's MiniSat Patch Series -- Copyright (c) 2015, Chanseok Oh

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
associated documentation files (the "Software"), to deal in the Software without restriction,
including without limitation the rights to use, copy, modify, merge, publish, distribute,
sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or
substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT
OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
**************************************************************************************************/

#ifndef MapleCOMSPS_SimpSolver_h
#define MapleCOMSPS_SimpSolver_h

#include "../core/Solver.h"
#include "../mtl/Queue.h"

namespace MapleCOMSPS {

//=================================================================================================

// For Gaussian elimination
class Xor
{
	vec<Var> vars;

  public:
	bool rhs;

	Xor(const Clause& c, bool _rhs)
		: rhs(_rhs)
	{
		for (int i = 0; i < c.size(); i++)
			vars.push(var(c[i]));
	}

	inline int size() const { return vars.size(); }
	inline const Var& operator[](int i) const { return vars[i]; }
};
struct XorScc
{
	vec<Xor*> xors;
	vec<Var> vars;
};

class SimpSolver : public Solver
{
  public:
	// Constructor/Destructor:
	//
	SimpSolver();
	SimpSolver(const SimpSolver& s);
	~SimpSolver();

	// Problem specification:
	//
	Var newVar(bool polarity = true, bool dvar = true);
	bool addClause(const vec<Lit>& ps);
	bool addEmptyClause();				 // Add the empty clause to the solver.
	bool addClause(Lit p);				 // Add a unit clause to the solver.
	bool addClause(Lit p, Lit q);		 // Add a binary clause to the solver.
	bool addClause(Lit p, Lit q, Lit r); // Add a ternary clause to the solver.
	bool addClause_(vec<Lit>& ps);
	bool substitute(Var v, Lit x); // Replace all occurences of v with x (may cause a contradiction).

	// Parallel support:
	//
	bool GE;

	// Variable mode:
	//
	void setFrozen(Var v, bool b); // If a variable is frozen it will not be eliminated.
	bool isEliminated(Var v) const;

	// Solving:
	//
	bool solve(const vec<Lit>& assumps, bool do_simp = true, bool turn_off_simp = false);
	lbool solveLimited(const vec<Lit>& assumps, bool do_simp = true, bool turn_off_simp = false);
	bool solve(bool do_simp = true, bool turn_off_simp = false);
	bool solve(Lit p, bool do_simp = true, bool turn_off_simp = false);
	bool solve(Lit p, Lit q, bool do_simp = true, bool turn_off_simp = false);
	bool solve(Lit p, Lit q, Lit r, bool do_simp = true, bool turn_off_simp = false);
	bool eliminate(bool turn_off_elim = false); // Perform variable elimination based simplification.
	bool eliminate_();
	void removeSatisfied();

	// Memory managment:
	//
	virtual void garbageCollect();

	// Generate a (possibly simplified) DIMACS file:
	//
#if 0
    void    toDimacs  (const char* file, const vec<Lit>& assumps);
    void    toDimacs  (const char* file);
    void    toDimacs  (const char* file, Lit p);
    void    toDimacs  (const char* file, Lit p, Lit q);
    void    toDimacs  (const char* file, Lit p, Lit q, Lit r);
#endif

	void disableSimplification() { use_simplification = false; }

	// Mode of operation:
	//
	bool parsing;
	int grow;			 // Allow a variable elimination step to grow by a number of clauses (default to zero).
	int clause_lim;		 // Variables are not eliminated if it produces a resolvent with a length above this limit.
						 // -1 means no limit.
	int subsumption_lim; // Do not check if subsumption against a clause larger than this. -1 means no limit.
	double
		simp_garbage_frac; // A different limit for when to issue a GC during simplification (Also see 'garbage_frac').

	bool use_asymm;	 // Shrink clauses by asymmetric branching.
	bool use_rcheck; // Check if a clause is already implied. Prett costly, and subsumes subsumptions :)
	bool use_elim;	 // Perform variable elimination.

	// Statistics:
	//
	int merges;
	int asymm_lits;
	int eliminated_vars;

  protected:
	// Helper structures:
	//
	struct ElimLt
	{
		const vec<int>& n_occ;
		explicit ElimLt(const vec<int>& no)
			: n_occ(no)
		{
		}

		// TODO: are 64-bit operations here noticably bad on 32-bit platforms? Could use a saturating
		// 32-bit implementation instead then, but this will have to do for now.
		uint64_t cost(Var x) const { return (uint64_t)n_occ[toInt(mkLit(x))] * (uint64_t)n_occ[toInt(~mkLit(x))]; }
		bool operator()(Var x, Var y) const { return cost(x) < cost(y); }

		// TODO: investigate this order alternative more.
		// bool operator()(Var x, Var y) const {
		//     int c_x = cost(x);
		//     int c_y = cost(y);
		//     return c_x < c_y || c_x == c_y && x < y; }
	};

	struct ClauseDeleted
	{
		const ClauseAllocator& ca;
		explicit ClauseDeleted(const ClauseAllocator& _ca)
			: ca(_ca)
		{
		}
		bool operator()(const CRef& cr) const { return ca[cr].mark() == 1; }
	};

	// Solver state:
	//
	int elimorder;
	bool use_simplification;
	vec<uint32_t> elimclauses;
	vec<char> touched;
	OccLists<Var, vec<CRef>, ClauseDeleted> occurs;
	vec<int> n_occ;
	Heap<ElimLt> elim_heap;
	Queue<CRef> subsumption_queue;
	vec<char> frozen;
	vec<char> eliminated;
	int bwdsub_assigns;
	int n_touched;

	// Temporaries:
	//
	CRef bwdsub_tmpunit;

	// Main internal methods:
	//
	lbool solve_(bool do_simp = true, bool turn_off_simp = false);
	bool asymm(Var v, CRef cr);
	bool asymmVar(Var v);
	void updateElimHeap(Var v);
	void gatherTouchedClauses();
	bool merge(const Clause& _ps, const Clause& _qs, Var v, vec<Lit>& out_clause);
	bool merge(const Clause& _ps, const Clause& _qs, Var v, int& size);
	bool backwardSubsumptionCheck(bool verbose = false);
	bool eliminateVar(Var v);
	void extendModel();

	void removeClause(CRef cr);
	bool strengthenClause(CRef cr, Lit l);
	bool implied(const vec<Lit>& c);
	void relocAll(ClauseAllocator& to);

	// Gaussian elimination:
	//
	bool gaussElim();

	bool searchXors(vec<Xor*>& /*out*/ xors);
	// Given XORs, compute SCCs in terms of vars.
	int computeVarSccs(vec<Var>& /*out*/ v2scc_id, vec<vec<Var>>& /*out*/ var_sccs, vec<Xor*>& xors) const;
	// Given var SCCs, compute SCCs in terms of XORs.
	void computeXorSccs(vec<XorScc*>& /*out*/ xor_sccs,
						const vec<Xor*>& xors,
						const vec<Var>& v2scc_id,
						vec<vec<Var>>& var_sccs,
						int upper_limit) const;
	bool performGaussElim(vec<XorScc*>& xor_sccs);

	int toDupMarkerIdx(const Clause& c);
	void addBinNoDup(Lit a, Lit b);
};

//=================================================================================================
// Implementation of inline methods:

inline bool
SimpSolver::isEliminated(Var v) const
{
	return eliminated[v];
}
inline void
SimpSolver::updateElimHeap(Var v)
{
	if (!use_simplification)
		return;
	/* assert(use_simplification); */
	// if (!frozen[v] && !isEliminated(v) && value(v) == l_Undef)
	if (elim_heap.inHeap(v) || (!frozen[v] && !isEliminated(v) && value(v) == l_Undef))
		elim_heap.update(v);
}

inline bool
SimpSolver::addClause(const vec<Lit>& ps)
{
	ps.copyTo(add_tmp);
	return addClause_(add_tmp);
}
inline bool
SimpSolver::addEmptyClause()
{
	add_tmp.clear();
	return addClause_(add_tmp);
}
inline bool
SimpSolver::addClause(Lit p)
{
	add_tmp.clear();
	add_tmp.push(p);
	return addClause_(add_tmp);
}
inline bool
SimpSolver::addClause(Lit p, Lit q)
{
	add_tmp.clear();
	add_tmp.push(p);
	add_tmp.push(q);
	return addClause_(add_tmp);
}
inline bool
SimpSolver::addClause(Lit p, Lit q, Lit r)
{
	add_tmp.clear();
	add_tmp.push(p);
	add_tmp.push(q);
	add_tmp.push(r);
	return addClause_(add_tmp);
}
inline void
SimpSolver::setFrozen(Var v, bool b)
{
	frozen[v] = (char)b;
	if (use_simplification && !b) {
		updateElimHeap(v);
	}
}

inline bool
SimpSolver::solve(bool do_simp, bool turn_off_simp)
{
	budgetOff();
	assumptions.clear();
	return solve_(do_simp, turn_off_simp) == l_True;
}
inline bool
SimpSolver::solve(Lit p, bool do_simp, bool turn_off_simp)
{
	budgetOff();
	assumptions.clear();
	assumptions.push(p);
	return solve_(do_simp, turn_off_simp) == l_True;
}
inline bool
SimpSolver::solve(Lit p, Lit q, bool do_simp, bool turn_off_simp)
{
	budgetOff();
	assumptions.clear();
	assumptions.push(p);
	assumptions.push(q);
	return solve_(do_simp, turn_off_simp) == l_True;
}
inline bool
SimpSolver::solve(Lit p, Lit q, Lit r, bool do_simp, bool turn_off_simp)
{
	budgetOff();
	assumptions.clear();
	assumptions.push(p);
	assumptions.push(q);
	assumptions.push(r);
	return solve_(do_simp, turn_off_simp) == l_True;
}
inline bool
SimpSolver::solve(const vec<Lit>& assumps, bool do_simp, bool turn_off_simp)
{
	budgetOff();
	assumps.copyTo(assumptions);
	return solve_(do_simp, turn_off_simp) == l_True;
}

inline lbool
SimpSolver::solveLimited(const vec<Lit>& assumps, bool do_simp, bool turn_off_simp)
{
	assumps.copyTo(assumptions);
	return solve_(do_simp, turn_off_simp);
}

//=================================================================================================
}

#endif
